feat: add Venice AI provider integration

Venice AI is a privacy-focused AI inference provider with support for
uncensored models and access to major proprietary models via their
anonymized proxy.

This integration adds:

- Complete model catalog with 25 models:
  - 15 private models (Llama, Qwen, DeepSeek, Venice Uncensored, etc.)
  - 10 anonymized models (Claude, GPT-5.2, Gemini, Grok, Kimi, MiniMax)
- Auto-discovery from Venice API with fallback to static catalog
- VENICE_API_KEY environment variable support
- Interactive onboarding via 'venice-api-key' auth choice
- Model selection prompt showing all available Venice models
- Provider auto-registration when API key is detected
- Comprehensive documentation covering:
  - Privacy modes (private vs anonymized)
  - All 25 models with context windows and features
  - Streaming, function calling, and vision support
  - Model selection recommendations

Privacy modes:
- Private: Fully private, no logging (open-source models)
- Anonymized: Proxied through Venice (proprietary models)

Default model: venice/llama-3.3-70b (good balance of capability + privacy)
Venice API: https://api.venice.ai/api/v1 (OpenAI-compatible)

src/commands/onboard-auth.ts

@@ -2,6 +2,10 @@ export {
   SYNTHETIC_DEFAULT_MODEL_ID,
   SYNTHETIC_DEFAULT_MODEL_REF,
 } from "../agents/synthetic-models.js";
+export {
+  VENICE_DEFAULT_MODEL_ID,
+  VENICE_DEFAULT_MODEL_REF,
+} from "../agents/venice-models.js";
 export {
   applyAuthProfileConfig,
   applyKimiCodeConfig,
@@ -12,6 +16,8 @@ export {
   applyOpenrouterProviderConfig,
   applySyntheticConfig,
   applySyntheticProviderConfig,
+  applyVeniceConfig,
+  applyVeniceProviderConfig,
   applyVercelAiGatewayConfig,
   applyVercelAiGatewayProviderConfig,
   applyZaiConfig,
@@ -39,6 +45,7 @@ export {
   setOpencodeZenApiKey,
   setOpenrouterApiKey,
   setSyntheticApiKey,
+  setVeniceApiKey,
   setVercelAiGatewayApiKey,
   setZaiApiKey,
   writeOAuthCredentials,